The IBM System/370 Model 168 and Model 158 were both announced on August 2, 1972. Prior 370 systems had not "offered

virtual storage In computing, virtual memory, or virtual storage, is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very ...

capability, which was to be a hallmark of the 370 line," and some said that the 168 and 158 were the first "real 370" products. By contrast, "in 1972, the System/370 Advanced Function was released and had new Address Relocation Hardware and now supported four new operating systems (

VM/370 VM (often: VM/CMS) is a family of IBM virtual machine operating systems used on IBM mainframes System/370, System/390, zSeries, System z and compatible systems, including the Hercules emulator for personal computers. Design The heart of t ...

DOS/VS Disk Operating System/360, also DOS/360, or simply DOS, is the discontinued first member of a sequence of operating systems for IBM System/360, System/370 and later mainframes. It was announced by IBM on the last day of 1964, and it was first del ...

OS/VS1 Operating System/Virtual Storage 1, or OS/VS1, is a discontinued IBM mainframe computer operating system designed to be run on IBM System/370 hardware. It was the successor to the Multiprogramming with a Fixed number of Tasks (MFT) option of Sys ...

, OS/VS2)." The 158 and 168 were withdrawn on September 15, 1980.

Features

Main memory

Main memory, which was four-way doubleword interleaved, could be 1 to 8

megabyte The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix ''mega'' is a multiplier of (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes ...

s, with offerings selectable in increments of one megabyte. The Model 168 used

semiconductor memory Semiconductor memory is a digital electronic semiconductor device used for digital data storage, such as computer memory. It typically refers to devices in which data is stored within metal–oxide–semiconductor (MOS) memory cells on a si ...

, rather than the

magnetic-core memory In computing, magnetic-core memory is a form of random-access memory. It predominated for roughly 20 years between 1955 and 1975, and is often just called core memory, or, informally, core. Core memory uses toroids (rings) of a hard magneti ...

used by the 370/165 introduced 2 years prior, resulting in a system that was faster and physically smaller than a Model 165.

System console

The newly introduced IBM 3066 Model 2

System A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its open system (systems theory), environment, is described by its boundaries, str ...

console Console may refer to: Computing and video games * System console, a physical device to operate a computer ** Virtual console, a user interface for multiple computer consoles on one device ** Command-line interface, a method of interacting with ...

, as with the 165's Model 1 * replaced "most switch, pushbutton, and indicator functions"among the few retained: "system clear" and "cooling reset alarm" * had a microfiche document viewer,the online manual has an extra dot: "d.ocument" a feature introduced for the 360/85's console.the 360/85 article includes a photo of same A console printer (up to 85 characters per second) to provide hard copy was optional when the console was in display mode, and required when it was in printer-keyboard mode.

Disk storage

The newly introduced Model 11 of IBM's 3330 family of disk drives, featuring removable disk packs, has double the capacity of the prior 100-megabyte offerings.It has the same number of platters but double the number of data cylinders.Similar to the

Massbus The Massbus is a high-performance computer input/output bus (computing), bus designed in the 1970s by Digital Equipment Corporation (DEC). The architecture development was sponsored by Gordon Bell and John Levy was the principal architect. The bu ...

/ DEC RP05/RP06 100 MB/200 MB capacities and number of cylinders. It can't be attached to a 370/165.

Multiprocessing

Both the 370/168 and the 370/158 had MP (multiprocessing) models that offered "tightly coupled

multiprocessing Multiprocessing (MP) is the use of two or more central processing units (CPUs) within a single computer system. The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them. The ...

. The 168 was described as having "two types of multiprocessing support" since it also offered attaching a second processing unit, an IBM 3062 Attached Processing Unit, which lacked access to Input/Output channels.

Extended precision Extended precision refers to floating-point number formats that provide greater precision than the basic floating-point formats. Extended-precision formats support a basic format by minimizing roundoff and overflow errors in intermediate value ...
floating-point

This feature adds support for 128-bit "hexadecimal" floating-point operands. It is standard on all 165 and 168 models, and is an "Optional (no-charge)" feature on the 370/158.

Emulation

The optional IBM 7070/7074 Compatibility Feature allowed the 168 to "run 7070 and 7074 programs at speeds that, in general, equal or exceed those of the original systems" and yet "not affect normal operation of System/370." Other listed options are: * 7080 Compatibility * 709/7090/7094 II Compatibility There is a limitation, however, described as:
"Note: Compatibility features are mutually exclusive."

System/370 Extended Facility

This optional facility of the 168-3 provides support for MVS/System Extensions (MVS/SE) and for the later MVS/System Product (MVS/SP).

168-1 & 168-3

The Third (June 1975) edition of IBM's 168 Guide introduced the 168-3.
"There are two versions of the Model 168: the Model 1 and the Model 3." IBM referred to the System/370 Model 168-3 as "the company's previous flagship" when comparing it and the then-new IBM 3033. The 168-3 CPU's internal performance has been described as 5–13% faster than the 168-1.

Notes

References

{{DEFAULTSORT:IBM System 370 Model 168 IBM System/360 mainframe line Computer-related introductions in 1972